1. Field of the Invention
This invention relates to a technique for imaging raw samples carried together with liquid in a sample container and particularly relates to the illumination of the raw samples.
2. Description of the Related Art
In medical and bioscience experiments, liquid or gel-like fluid (e.g. culture fluid, culture medium or the like) is poured into each well of a plate-like sample container (e.g. called a microplate, a microtiter plate or the like) on which a multitude of recesses, for example, also called wells are arranged, and cells and the like cultured here are observed and measured as samples. In recent years, samples have been imaged and converted into data by a CCD camera or the like, and various image processing techniques have been applied to this image data for observation and analysis.
In such an imaging apparatus, there is a problem that illumination light is refracted by the meniscus of a liquid surface and the brightness of an image becomes insufficient particularly at peripheral edge parts of the wells. To deal with this problem, in a technique described in JP 2015-118036A previously disclosed by the applicant of this application, an imaging optical system has an object-side hypercentric property, whereby light having a propagation direction bent in a direction away from an optical axis by refraction can be efficiently collected.